We propose to (1) characterize the physiochemical nature of the unconventional agents producing spongiform encephalopathies in animals (scrapie and transmissible mink encephalopathy) and man (Creutzfeldt-Jakob disease), (2) to study the pathogenesis of these infections in suitable hosts, and (3) to investigate the epidemiologic interrelationships between the human and animal encephalopathies.